Spherical carbons in which 60, 70, 76, 78, 82, or 84 carbon atoms are bonded in a spherical shape to form a cluster (molecular aggregate) are referred to as fullerenes. Fullerenes have drawn considerable attention as materials that have excellent functionalities, such as magnetic properties, superconducting properties, nonlinear optical effects, and catalysis.
When such fullerenes in a powdery state are left in the air, they will become insoluble in solvent in several days. By simply Ar-substituting the fullerenes, the components that are insoluble in solvent will increase in several days. When fullerenes are dissolved in an organic solvent as well, the insoluble components will be formed because of, for example, dissolved oxygen and moisture. In the case of solutions in which such fullerenes are dissolved in an organic solvent, the solutions need to be transported according to the handing for the organic solvent. Moreover, the fullerenes generally show a low solubility to solvent (e.g., several milligrams to several ten milligrams per milliliter), so a large amount of solvent is necessary in order to transport a certain amount of them in a solution form. For example, in order to dissolve 10 g of a fullerene that has a solubility of 1 mg/mL, 10 L of solvent is required.
Thus, a problem with the fullerene has been that storage thereof is difficult, and if the fullerene is stored without taking any measures, alteration occurs (one that has been soluble in solvent becomes insoluble). Another problem has been that although it may be stored in a solution, a large amount of solvent is necessary in that case due to poor solubility of the fullerene.
However, no storage method for fullerene that can prevent alteration of fullerene has been known to date. For example, publicly known literatures related to fullerenes describe that alteration of fullerene occurs because of oxygen and ultraviolet rays, but in reality, they do not mention any storage method. (See Patent Document 1 below.)